1. Technical Field
The present invention relates to a method for manufacturing a semiconductor substrate and a method for manufacturing an electro-optical device.
2. Related Art
Electro-optical devices such as liquid crystal devices and organic electroluminescent (hereinafter called “EL”) devices that include a structure provided with semiconductor elements such as thin-film transistors (hereinafter called “TFT”) on a substrate are generally known. In most cases, manufacturing the semiconductor substrate fitted with such semiconductor elements requires high-temperature processing. Accordingly, forming an electro-optical device including the semiconductor elements on the substrate can deform the substrate by heat, damage peripheral circuit elements, and lower product life. As a result, characteristics of the electro-optical device can be reduced.
In recent years, transfer methods for manufacturing electro-optical devices have been proposed that employ a conventional semiconductor manufacturing technology including high-temperature processing in order to provide semiconductor elements such as TFT on a heat-resisting base substrate, then separate an element-forming film (layer) fitted with the TFT from the base substrate, and then join the film on a wiring substrate have been disclosed (see Japanese Unexamined Patent Publication No. 2003-031778, for example). Using this transfer technology allows semiconductor elements to be provided on, for example, a plastic substrate that has relatively low heat resistance. Consequently, it is possible to enhance the design versatility of such electro-optical devices and avoid exposing peripheral circuit elements to high-temperature processing, and thereby reducing heat deformation of the substrate and damage of the circuit elements and providing desirable electro-optical devices.
According to Japanese Unexamined Patent Publication No. 2003-031778, conductive particles are printed and arranged on a bump formed on a wiring substrate, and a TFT substrate is further transferred thereto with a curing resin therebetween. Then the wiring substrate and TFT are joined by heat and pressure. This transfer technology, however, can cause an open defect with poor conductivity of the TFT in joining the wiring substrate and TFT because of inaccurate bump heights, inaccurate printing of the conductive particles (printing amount, shape, alignment), substrate bending caused by transferring under heat and pressure, poor trapping of the conductive particles, and so forth. In addition, transferring under more heat and pressure in order to avoid such an open defect can damage the TFT.
Taking the above problems into account, the present invention aims to provide a method for manufacturing a semiconductor substrate that ensures conductivity between an element and wiring substrate without damaging the element, and also provide a method for manufacturing an electro-optical device.